People are plundering the world's resources at a pace that outstrips the planet's capacity to sustain life, the environmental group WWF said Thursday.
In its regular Living Planet Report, the World Wide Fund for Nature said humans currently consume 20 percent more natural resources than the earth can produce.
Consumption of fossil fuels such as coal, gas and oil increased by almost 700 percent between 1961 and 2001, it said. But the planet is unable to move as fast to absorb the resulting carbon-dioxide emissions that degrade the earth's protective ozone layer.
"We are spending nature's capital faster than it can regenerate," said WWF chief Claude Martin, launching the conservation body's 40-page study.
"We are running up an ecological debt which we won't be able to pay off unless governments restore the balance between our consumption of natural resources and the earth's ability to renew them."
Populations of terrestrial, freshwater and marine species fell on average by 40 percent between 1970 and 2000, the study said. It cited destruction of natural habitats, pollution, overfishing and the introduction by humans of nonnative animals, such as cats and rats, which often drive out indigenous species.
"The question is how the world's entire population live with the resources of one planet," said Jonathan Loh, one of the report's authors.
The study, WWF's fifth since 1998, examines the "ecological footprint" — or environmental impact — of the planet's 6.1 billion-strong population.
To calculate the average size of each person's footprint, it measures land use, pollution, energy consumption, and the level of carbon-dioxide emissions. It then determines how many hectares of land are necessary to produce or absorb what one person uses.
The impact of an average North American is double that of a European, but seven times that of the average Asian or African.
Overall, the biggest culprits are the residents of the United Arab Emirates, followed by the United States, Kuwait, Australia and Sweden. The least-damaging are residents of Afghanistan, Somalia, Haiti, Tajikistan and Bangladesh.
In the United States, a person consumes about 10 hectares worth. In China, a person consumes less than two hectares worth.
Rich nations tread heavily on poorer countries, said Mathis Wacknagel, head of the Global Footprint Network, a grouping including WWF. For example, Western demand for of Asia's palm oil and soybeans from South America has fueled destruction of natural habitats in those regions.
The study also warned of increasing pressure on the planet's resources amid spiraling consumption in Asia, led by fast-growing China and India.
"We can consume energy in a way that's harmful or in a way that's sustainable," Loh told reporters. "The technologies are available to enable the world's population to live within the capacity of one planet."
The report suggests efforts to control world population while both reducing consumption and making it more equal across countries. Governments, businesses and consumers should switch to energy efficient technology, such as solar power, Loh said, adding that high oil prices may help focus their minds.
"It's not a question of how much oil is left," he said. "The question we should be asking is how much fossil fuel consumption the earth can sustain. The earth has a limited capacity."